The invention relates to a pump for fluid media, more particularly to a cooling water pump for internal combustion engines with an electric motor configured as a disk armature for actuating the pump, the electric motor being directly connected to an impeller of the pump. Depending on the purpose intended to be served, diverse requirements are placed on pumps. In electric coolant pumps for example, absolute reliability is an important criterion since, upon failure of the cooling system, important damage may be caused to the internal combustion engine. Furthermore, in an effort to reduce cost and to achieve the greatest freedom from component parts is an aim that is strived for. Further directions relate to the available mounting space, which is restricted in many cases.
DE 196 17 495 A is directed to a fuel pump for motor vehicles which is provided with a rotor that serves as a disk armature of an electric motor on the one side and as a pump impeller on the other side. Blades for lifting the medium are configured for this purpose on the outer circumference of the rotor. Such a pump only permits to achieve restricted efficiency as the pump geometry is not very optimal. Furthermore, with the classic disk armature, the current has to be supplied to the electric windings in the disk by way of brushes that have to be sealed from the flowing medium.
DE 16 13 626 A or DE 25 56 631 A describe electric motors which actuate pumps or fans and in which a winding is arranged in the region of the impeller. The torque of such motors is limited, though, and fail-safe cooling water pumps for motors of motor vehicles cannot be produced easily.
It is the object of the present invention to provide a pump that avoids these drawbacks, has a simple structure while having the smallest possible size, and provides fall-safe operation.
The solution to these objects in accordance with the invention is achieved in that a driving flange projects radially outwardly on the outer circumference of the pump""s impeller, with magnets or windings molded therein for the contactless drive of the impeller. Such a pump has but one movable component part, which is the impeller with the driving flange molded thereto. The large diameter of the driving flange permits a great driving torque to be achieved, but the dimension of the pump in the axial direction is very small. The electric motor of the pump in axial direction is very small. The electric motor of the pump in accordance with the invention is not configured as a classic disk armature in which flat pressed magnet coils, which are supplied with current via brushes, are arranged in the disk-shaped rotor, but as a permanent magnet DC motor or as a three-phase asynchronous motor. In both cases, the torque is provided by an outer magnetic field produced in the stator. Assuming that the motor of the pump is in principle driven from DC energy, the rotating field is produced by an electronic circuit. The additional advantage thereof is that the performance of the pump can be very readily adjusted according to the specific needs.
In a particularly preferred variant of the invention, the electric motor is configured to operate in a xe2x80x9cwetxe2x80x9d environment. This means that the movable parts within the pump are not sealed, i.e., the gap between stator and rotor of the pump is also flooded with the medium to be delivered.
In another particularly preferred variant of the invention, the impeller is designed as an axial-radial flow impeller that is provided with a flange face to which blades are molded, the driving flange being arranged radially outside of the flange face. In this context, it is particularly preferred to have the driving flange offset in axial direction. This makes it possible to freely configure the delivery housing radially outside of the impeller and to concurrently provide a part of the stator between the delivery housing and the driving flange.
The structure of the pump of the invention is particularly simple and inexpensive if the impeller is made of plastic material and if the magnets are molded thereto by injection molding in the form of inserts. Such a solution is also characterized by a robust mechanical structure. It should be born in mind though that, to prevent demagnetisation, the magnets can only be heated within permissible limits. As an alternative, the magnets can also be magnetized in situ after the impeller is manufactured so that the injection molding process is not subject to any limitations.